The Paducah Gaseous Diffusion Plant (PGDP) is located in Western Kentucky, about 10 miles west of the City of Paducah. It currently employs approximately 1700 workers; some 8,000 individuals have worked at the plant since it was opened in 1952. The plant is located in a rural area, adjacent to protected conservation, wildlife and recreation areas. The primary function of the PGDP has been to produce enriched uranium for use by commercial reactors or as feed material for other plants that further enrich the uranium. Workers, government officials and the surrounding community have raised concerns about potential health effects from current and past exposures at the plant. The studies proposed here will complete an ongoing mortality investigation to help address those concerns, by combining work histories with historical exposure data to create an exposure metric for each worker at the plant, throughout the history of the facility. In Specific Aim 1, we will validate the worker roster against other existing name lists and source documents. In Specific Aim 2, we will develop a comprehensive list of jobs and job histories for the workforce from paper records and electronic files. In Specific Aim 3, we will create a Job Exposure Matrix for chemical and radiation exposures throughout the history of the plant. In Specific Aim 4, we will link the Work History data with the Job Exposure Matrix to estimate individual worker exposure metrics. In Specific Aim 5, we will evaluate worker Mortality for relationships with workplace exposures using standardized mortality ratios and risk assessment approaches. In Specific Aim 6, we will communicate the study results to employees and management. The overarching goal of these investigations is to evaluate the impact of historical exposures on worker mortality. The PGDP is the only remaining gaseous diffusion plant in the US that has not undergone a comprehensive occupational health study. The data generated by the PGDP investigations will be available to merge with the two prior studies at the Portsmouth and Oak Ridge gaseous diffusion plant facilities. The Paducah data will add substantially to the statistical power of the combined database to address the pressing health concerns of uranium enrichment workers.